1. Field of the Invention
The present invention relates to a system, method and program for avoiding a collision between movers. The present invention relates also to a system, method and program for detecting a position of a mover traveling (moving) on a traveling track.
2. Description of the Related Art
A plurality of movers included in a library system travel on the same travelling track. Hence, it is necessary to control the plurality of movers not to collide with each other.
A method of avoiding a collision between two movers travelling back and forth on the same travelling track (path) is disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H3-100809. Particularly, according to the disclosed methods two movers are avoided colliding with each other, as will be described below.
A plurality of position indicators are arranged at equal intervals on the travelling track. A reader for reading the position indicators is installed in each of the movers. The reader reads the position indicators, at the time each mover passes each position indicator.
The position of each position indicator which is read by the reader is identified as a position of the mover. The position of the mover is updated every time the reader newly reads the position indicator.
The time period since the reader reads out a particular position indicator until it reads the next position indicator is measured. The velocity of the mover is obtained, based on the distance between the position indicators and the measured time.
Based on the position and velocity of each mover, it is determined whether there is a great chance of collision between two movers. In the case where it is determined that there is a great chance of collision therebetween, the two movers are stopped in an emergency
According to this method, the collision of the movers may not successfully he avoided.
As explained above, the position and velocity of each mover is acquired every time the mover passes each position indicator. In other words, according to the above method, the position and velocity of the mover staying between two position indicators can not be obtained.
For example, the mover slows down near the its target point. In the case where the mover slows down, it takes quite a long time that the mover passes the next position indicator. The position and velocity of the mover can not be updated until it passes the next position indicator. Hence, the obtained position and velocity of the mover may be far from the actual position and velocity.
In this case, it is impossible to determine whether there is a great chance that two neighboring movers will collide with each other. According to the method disclosed in the publication, the collision between the movers can not successfully be avoided.
The entire contents of Unexamined Japanese Patent Application KOKAI Publication No. H3-100809 are incorporated herein by reference.
The present invention has been made in consideration of the above. It is accordingly an object of the present invention to provide a system, method and program for avoiding a collision between movers.
Another object thereof is to provide a system, method and program for detecting positions of movers travelling on a travelling track.
In order to attain the above objects, according to the first aspect of the present invention, there is provided a collision avoidance system which avoids a collision between a plurality of movers traveling on a path divided into sections of various lengths, the system comprising:
a position/velocity calculator which estimates a position and velocity for each of the plurality of movers based upon one of a first position and first velocity for each of the plurality of movers which passes a boundary between adjacent sections and a second position and second velocity for each of the plurality of movers which are traveling within any of the sections based upon a previous of the first position and first velocity for each of the plurality of movers which are traveling within any of the sections;
a collision-chance determiner which determines whether there is a chance that each two neighboring movers will collide with each other, using the estimates of position and velocity; and
an emergency stopper which stops two neighboring movers when the collision-chance determiner determines that there is a chance of collision between the two neighboring movers.
According to this invention, the collision between the movers can be avoided.
The position/velocity calculator may include:
a boundary calculation unit which obtains the first position and first velocity of each of the plurality of movers in a case where each of the plurality of movers passes a boundary between the adjacent sections; and
a section-calculation unit which obtains the second position and second velocity of each of the plurality of movers in any of the sections, based on a modeled movement, using the first position and first velocity obtained by the boundary calculation unit.
Each of the sections may be identified based on its address;
the collision avoidance system may further include
an address detector which detects first addresses of the sections in which the plurality of movers are traveling; and
an address-difference determiner which
determines whether the first addresses detected by said address detector are different respectively from second addresses detected by said address detector a predetermined period ago,
determines, in a case where it is determined that the first address is different from the second address, that any of the plurality of movers traveling in the section with the first address has passed a boundary between adjacent sections, and
determines, in a case where it is determined that the first address is not different from the second address, that any of the plurality of movers is traveling in the section with the first address,
the boundary calculation unit obtains the first position and first velocity of any of the movers traveling in the section with the first address, in the case where it is determined that the first address is different from the second address; and
the section-calculation unit may obtain the second position and second velocity of any of the movers traveling in the section with the second address, in the case where it is determined that the first address is not different from the second address.
The movement may be expressed in a form of a model, wherein the mover travels with a constant velocity and slows down at a constant acceleration.
The movement may be expressed in a form of a model, wherein the mover accelerates at a constant acceleration, travels with a constant velocity and slows down at a constant acceleration.
The collision avoidance system may further include a memory unit which stores association information representing the address and boundary positions of each of the sections, in association each other; and
the boundary calculation unit may include
a position calculation unit which obtains, as a position of the mover, one of the boundary positions of the section in which the mover is traveling and having the first address, and
a velocity calculation unit which obtains a velocity of the mover traveling in the section having the first address, by dividing a length of one of the plurality of sections which has the second address by a time period since said address-difference determiner determines that the first address is different from the second address until a next time the address-difference determiner determines that the first address is different from the second address.
The position calculation unit may obtain, as a position of the mover, one of the boundary positions that the mover has passed, of the boundary positions of the section in which the mover is traveling.
In order to attain the above objects, according to the second aspect of the present invention, there is provided a position detector comprising:
a first calculation unit which obtains a position and velocity of a mover traveling on a path divided into sections of various lengths, in a case where the mover passes a boundary between adjacent sections; and
a second calculation unit which obtains a position of the mover traveling in any of the sections, using a previous position and velocity obtained by said first calculation unit.
According to this invention, the collision between movers can be avoided.
The second calculation unit may obtain the position of the mover traveling in any of the sections, based on a modeled movement, using the previous position and velocity obtained by said first calculation unit.
Each of the sections may be identified based on its address;
the position detector may further include
an address detector which detects a first address of the section in which the mover is traveling, and
an address-difference determiner which
determines whether the first address detected by the address detector is different from a second address detected by the address detector a predetermined period ago,
determines, in a case where it is determined that the first address is different from the second address, that the mover traveling in the section with the first address has passed a boundary between adjacent sections, and
determines, in a case where it is determined that the first address is not different from the second address, that the mover is traveling in a section with the first address;
the first calculation unit may obtain the position and velocity of the mover traveling in the section with the first address, in the case where it is determined that the first address is different from the second address; and
the second calculation unit may obtain the position of the mover traveling in the section with the second address, in the case where it is determined that the first address is not different from the second address.
The movement may be expressed in a form of a model, wherein the mover travels with a constant velocity and slows down at a constant acceleration.
The movement may be expressed in a form of model, wherein the mover accelerates at a constant acceleration, travels with a constant velocity and slows down at a constant acceleration.
The position detector may further include memory unit which stores association information representing the address and boundary positions of each of the sections, in association each other; and
the first calculation unit may include
a position calculation unit which obtains, as a position of the mover, one of the boundary positions of the section in which the mover is traveling and having the first address, and
a velocity calculation unit which obtains a velocity of the mover traveling in the section having the first address, by dividing a length of one of the plurality of sections which has the second address by a time period since said address-difference determiner determines that the first address is different from the second address until a next time the address-difference determiner determines that the first address is different from the second address.
The position calculation unit may obtain, as a position of the mover, one of the boundary positions that the mover has passed, of the boundary positions of the section in which the mover is traveling.
In order to attain the above objects, according to the third aspect of the present invention, there is provided a collision avoidance method of avoiding a collision between a plurality of movers traveling on a path divided into sections of various lengths, said method comprising:
estimating a position and velocity for each of the plurality of movers based upon one of a first position and first velocity for each of the plurality of movers which a boundary between adjacent sections and a second position and second velocity for each of the plurality of movers which are traveling within any of the sections based upon a previous of the first position and first velocity for each of the plurality of movers which are traveling within any of the sections;
determining whether there is a chance that each two neighboring movers will collide with each other, using the estimates; and
stopping two neighboring movers when there is a chance of collision between the two neighboring movers.
The estimating the position and velocity may include:
obtaining a previous first position and first velocity of each of the plurality of movers in a case where each of the plurality of movers passes the boundary between the adjacent sections; and
obtaining the second position and second velocity of each of the plurality of movers in any of the sections, based on a modeled movement of a mover, using the previous first position and first velocity obtained in the case where each of the plurality of movers passes the boundary therebetween.
Each of the sections may be identified based on its address;
the collision avoidance method may further include
detecting first addresses of the sections in which the plurality of movers are traveling, and
determining whether the detected first addresses are different respectively from second addresses detected a predetermined period ago,
determining, in a case where it is determined that the first address is different from the second address, that any of the plurality of movers traveling in the section with the first address has passed a boundary between adjacent sections, and
determining, in a case where it is determined that the first address is not different from the second address, that any of the plurality of movers is traveling in the section with the first address;
the obtaining the first position and first velocity of each of the plurality of movers may include obtaining the first position and first velocity of any of the movers traveling in the section with the first address, in the case where it is determined that the first address is different from the second address; and
the obtaining the second position and second velocity of each of the plurality of movers based on the modeled movement may include obtaining the second position and second velocity of any of the movers traveling in the section with the second address, in the case where it is determined that the first address is not different from the second address.
The movement may be expressed in a form of a model, wherein the mover travels with a constant velocity and slows down at a constant acceleration.
The movement may be expressed in a form of a model, wherein the mover accelerates at a constant acceleration, travels with a constant velocity and slows down at a constant acceleration.
The collision avoidance method may further include storing association information representing the address and boundary positions of each of the sections, in association each other; and
the obtaining the first position and first velocity may include
obtaining, as a position of the mover, one of the boundary positions of the section in which the mover is traveling and having the first address, and
obtaining a velocity of the mover traveling in the section having the first address, by dividing a length of one of the plurality of section which has the second address by a time period since it is determined that the first address is different from the second address until it is determined that the first address is different from the second address.
The obtaining, as the position of the mover, the one of the boundary positions of the section may include obtaining, as a position of the mover, one of the boundary positions that the mover has passed, of the boundary positions of the section in which the mover is traveling.
In order to attain the above objects, according to the fourth aspect of the present invention, there is provided a position detecting method comprising:
obtaining a first position and first velocity of a mover traveling on a path divided into sections of various lengths, in a case where the mover passes a boundary between adjacent sections; and
obtaining a second position and second velocity of the mover includes obtaining a position of the mover traveling in any of the sections, using a previously obtained first position and first velocity.
The obtaining the second position and second velocity of the mover may include obtaining a position of the mover traveling in any of the sections, based on a modeled movement of the mover, using the previously obtained first position and first velocity.
Each of the sections may be identified based on its address;
the position detecting method may further include
detecting a first address of the sections in which the mover is traveling, and
determining whether the detected first address is different from a second address detected a predetermined period ago,
determining, in a case where it is determined that the first address is different from the second address, that the mover traveling in the section with the first address has passed a boundary between adjacent sections, and
determining, in a case where it is determined that the first address is not different from the second address, that the mover is traveling in the section with the first address;
the obtaining the first position and first velocity of the mover may include obtaining the first position and first velocity of the mover traveling in the section with the first address, in the case where it is determined that the first address is different from the second address; and
the obtaining the second position and second velocity of the mover may include obtaining the second position and second velocity of the mover traveling in the section with the second address, in the case where it is determined that the first address is not different from the second address.
The movement may be expressed in a form of a model, wherein the mover travels with a constant velocity and slows down at a constant acceleration.
The movement may be expressed in a form of a model, wherein the mover accelerates at a constant acceleration, travels with a constant velocity and slows down at a constant acceleration.
The position detecting method may further include storing association information representing the address and boundary positions of each of the sections, in association each other; and
the obtaining then first position and first velocity of the mover may include;
obtaining, as the first position of the mover, one of the boundary positions of the section in which the mover is traveling and having the first address, using the association information, and
obtaining the first velocity of the mover traveling in the section having the first address, by dividing a length of one of the plurality of sections which has the second address by a time period since it is determined that the first address is different from the second address until it is determined that the first address is different from the second address.
The obtaining, as a position of the mover, the one of the boundary positions of the section may include obtaining, as a position of the mover, one of the boundary positions that the mover has passed, of the boundary positions of the section in which the mover is traveling.
In order to attain the above objects, according to the fifth aspect of the present invention, there is provided a program for controlling a computer to function as a collision avoidance system which avoids a collision between a plurality of movers traveling on a path divided into sections of various lengths, said system comprising:
a position/velocity calculator which estimates a position and velocity of each of the plurality of movers based upon one of a first position and first velocity for each of the plurality of movers which passes a boundary between adjacent sections and a second position and second velocity for each of the plurality of movers which are traveling within any of the sections based upon a previous of the first position and first velocity for each of the plurality of movers which are traveling within any of the sections;
a collision-chance determiner which determines whether there is a chance that each two neighboring movers will collide with each other, using the estimates; and
an emergency stopper which stops two neighboring movers that the collision-chance determiner determines that there is a chance of collision between the two neighboring movers.
In order to attain the above objects, according to the sixth aspect of the present invention, there is provided a program for controlling a computer to function as a position detector comprising:
a first calculation unit which obtains a position and velocity of a mover traveling on a path divided into sections of various lengths, in a case where the mover passes a boundary between adjacent sections; and
a second calculation unit which obtains a position of the mover traveling in any of the sections, using a previous position and velocity obtained by the first calculation unit.